Interface-Engineered Co@Co3O4@NC Nanoparticles on BiVO4 Photoanodes for Efficient Charge Transfer and Solar Water Oxidation

The employment of Co-based cocatalysts in BiVO4 (BVO) photoanodes is still suffering from inefficient hole transfer to active sites and sluggish charge kinetic processes. To address this issue, we designed a hierarchical dual-shell Co@Co3O4@NC (Co-DS) cocatalyst synthesized via the controlled pyrolysis of CoCo Prussian blue analogs under micro-oxygen conditions. The designed hierarchical structure consists of a graphitic carbon shell that encases the Co3O4 interlayer, which is abundant in OER-active sites, coupled with a metallic Co core that enhances hole accumulation and charge transfer across interfaces. The optimized Mo-BVO/Co-DS photoanode achieves a photocurrent density of 4.95 mA/cm2 at 1.23 VRHE, representing a 129% enhancement over pristine BVO (2.16 mA/cm2). This work provides fundamental insights into the design principles of metal-oxide-based cocatalysts for overcoming efficiency limitations in photochemical water oxidation.